Noise processing unit for a motor vehicle

Abstract

The present subject matter relates to an exhaust system for a motor vehicle having a noise treatment unit (225), wherein the noise treatment unit acts as a muffler. The noise treatment unit (225) is part of the exhaust system (102) and is connected to an internal combustion engine (101). The noise treatment unit (225) includes one or more intermediate chambers (311) which are selectively physically disposed between a plurality of first chambers (301, 302). One or more second chambers (321) are disposed after the plurality of first chambers (301, 302). The noise treatment unit (225) is configured to direct exhaust gas flow through the plurality of first chambers (301, 302), then through the one or more intermediate chambers (311), and then through the one or more second chambers (321). The noise treatment unit (225) occupies less space and provides effective noise attenuation.

Description

Technical Field

[0001] The present subject matter relates to a noise processing unit for a motor vehicle, and more particularly but not exclusively to a noise processing unit for a two - or three - wheel motor vehicle. Background Art

[0002] Generally, a motor vehicle powered by an internal combustion (IC) engine is equipped with an exhaust system that is connected to the exhaust port of the IC engine. The exhaust system is used to discharge the exhaust gases into the atmosphere, where the exhaust gases are generated due to the combustion of an air - fuel mixture in one or more combustion chambers of the IC engine of the motor vehicle and include carbon monoxide, hydrocarbons, nitrogen oxides, etc. In addition to processing the exhaust gases, the exhaust system is also used to attenuate the noise generated by the combustion process.

[0003] Generally, in some fun and adventurous applications such as racing, noisy motor vehicles may be preferred, where noise attenuation is not crucial. However, in commuting applications, considering noise pollution and other requirements to be met in public places, the noise emitted from motor vehicles is inappropriate. Brief Description of the Drawings

[0004] The detailed description is described with reference to the accompanying drawings, which relate to a two - wheel motor vehicle as an embodiment of the present invention. However, the present invention is not limited to the described embodiments. In the figures, the same or similar numbers are all used to refer to features and components.

[0005] Figure 1 A left - hand view of an exemplary motor vehicle according to an embodiment of the present subject matter is shown.

[0006] Figure 2 A right - hand view of an exemplary internal combustion engine with an exhaust system according to an embodiment of the present subject matter is shown.

[0007] FIG. 3(a) shows a schematic diagram of a noise processing unit according to an embodiment of the present subject matter.

[0008] FIG. 3(b) shows a schematic cross - sectional view of a noise processing unit according to an embodiment of the present subject matter.

[0009] FIG. 3(c) depicts another cross - sectional view of a noise processing unit according to an embodiment of the present subject matter.

[0010] FIG. 3(d) shows an enlarged view of a part of the noise processing unit according to an embodiment of the present subject matter as shown in FIG. 3(c). Detailed Description

[0011] Typically, in order to make the exhaust sound quieter, motor vehicles employ various methods, such as increasing the surface area / volume of a part of the exhaust system, where the exhaust gas generally expands within a muffler. In some other solutions known in the art, multiple tailpipes or a split exhaust system are used. All of these methods increase the overall size of the exhaust system including the muffler. Generally, the above-mentioned solutions are implemented in large-capacity motor vehicles, such as four-wheel motor vehicles or multi-wheel motor vehicles with more than four wheels. Such motor vehicles have a larger body and have a scope for accommodating an even longer and larger split exhaust system. Attempts have been made to apply similar solutions to two-wheel or three-wheel motor vehicles with large capacities, which generally have a larger vehicle area or a longer wheelbase. However, for smaller commuter vehicles with a compact vehicle layout or a relatively small wheelbase, the above-mentioned solutions cannot be implemented. In addition, the foregoing solutions increase the manufacturing cost of the vehicle, so it is impractical to implement the foregoing solutions in low-cost and smaller-capacity motor vehicles.

[0012] For example, two-wheel motor vehicles generally have a bare appearance, at least at the rear. On such vehicles, various key components such as an IC engine are compactly encapsulated between the two wheels. Some two-wheel motor vehicles even have a storage space for carrying loads or goods, which requires additional useful space on the vehicle, and this space cannot be affected or reduced. In these vehicles, the exhaust system is carefully routed so as to keep it away from the key components of the motor vehicle as well as the rider, so it is generally arranged towards the rear of the vehicle to limit the dissipation of heat towards the key components or the rider and / or the rear seat. In some other attempts to solve this problem, a control valve is provided within the muffler to direct air through various pipes or chambers. Accommodating such a valve and such multiple channels requires additional volume within the muffler and also requires a mechanical or electronic actuator to control the valve, thereby increasing the cost of the system. The additional volume generated on the already compact motor vehicle increases the size of the exhaust system, which can interfere with other components of the motor vehicle or the rider on the rear seat. Moreover, the increase in the size of the exhaust system is also a challenge for the appearance and can make the appearance disproportionate, which is undesirable.

[0013] Therefore, in motor vehicles with an exhaust system design facing the foregoing contradictions related to space and layout, etc., providing an effective noise treatment unit such as a muffler is a challenge that exists. Figure 4 The curve A depicted in shows an exemplary attenuation curve of a general small-capacity motor vehicle at various frequencies. As can be seen, there are certain pulses and sharp rises and falls in the attenuation at different frequencies, while at other parts, the noise attenuation is almost negligible. This can make the exhaust noise very annoying due to improper attenuation, making it noisy for the rider and passersby.

[0014] Furthermore, an exhaust system or a muffler in a two - or three - wheeled motor vehicle has one or two mounting portions, which poses the main challenge in mounting such a complex exhaust system. For example, a mounting portion such as a mounting bracket serves as a connecting member between the muffler and the frame assembly or chassis of the motor vehicle. There may be material defects around the welding area where the mounting bracket is connected to the muffler, making this part of the muffler a heat - affected zone and prone to durability failures. Additionally, the welding temperature generally reaches 1000 °C, which affects the mechanical properties of the heat - affected zone and ultimately leads to unexpected failures, damaging the exhaust system - the noise exhaust system or reducing its performance.

[0015] Therefore, an exhaust system is needed that can provide noise attenuation under almost all operating conditions of an IC engine. The exhaust system should be compact so as to be implemented even in motor vehicles with a small wheelbase. Further, the exhaust system should be cost - effective and should be easy to install through rigid mountings without any modification to the existing frame assembly or chassis.

[0016] The exhaust system according to the present invention includes a noise - handling unit having a compact configuration accommodated on a compact motor vehicle. In one embodiment, the noise - handling unit includes a plurality of chambers configured to effectively attenuate noise across different frequencies without taking up too much space.

[0017] In one embodiment, the noise - handling unit includes a plurality of first chambers, one or more second chambers, and one or more intermediate chambers. The plurality of first chambers substantially form an upstream chamber. One or more intermediate chambers are selectively physically disposed between the plurality of first chambers. One or more second chambers form a downstream chamber. The noise - handling unit is configured to direct the exhaust gas to flow through the plurality of first chambers, then through one or more intermediate chambers and through one or more second chambers for achieving effective noise attenuation across a wide frequency range.

[0018] In one embodiment, the exhaust gas passes through a large number of first chambers and then through the intermediate chamber. For example, in the case of two first chambers, the noise - reduction unit or the noise - handling unit can be configured such that the exhaust gas passes through the first chambers and then through one or more intermediate chambers.

[0019] In one embodiment, one or more intermediate chambers include a cumulative volume that is less than the cumulative volume of either of the plurality of first chambers and the one or more second chambers. Thus, the first chambers with a larger volume can achieve the expansion of the exhaust gas entering the noise - handling unit at a faster speed. The larger first chambers can achieve the reduction of energy and the corresponding noise due to effective expansion.

[0020] In one embodiment, an intermediate chamber with a smaller volume is configured to act on large-frequency waves, which are attenuated herein due to substantial changes in area and volume. These chambers are configured to generate internally reflected relative-phase sound waves of various frequencies, which are selectively canceled across the chambers, thereby producing a desired sound effect.

[0021] In one embodiment of the present invention, one or more intermediate chambers are selectively disposed between a plurality of first chambers in a predetermined layout. The one or more intermediate chambers are configured to change the flow direction of the exhaust gas in two or more directions. This increases the travel path of the exhaust gas, thereby enhancing the dissipation of thermal energy.

[0022] In one embodiment, a plurality of first chambers, one or more intermediate chambers, and one or more second chambers are adjacently disposed along the axis of the noise treatment unit. Since each chamber is disposed adjacent to another chamber along the axis, any expansion of dimensions is avoided, such as in the vertical direction, thereby not affecting the position of the current rear seat footrest and the positions of other key components. Thus, by substantially maintaining the cross-sectional area of the unit, at least two direction changes of the exhaust gas flow are even generated, and the present subject achieves effective noise attenuation.

[0023] In one embodiment, one or more intermediate chambers of the noise treatment unit include at least one intermediate chamber substantially disposed at the middle of the noise treatment unit. In one embodiment, at least one intermediate chamber is formed by a first baffle and a second baffle, and the baffles will be disposed near each other to form a smaller volume, and due to the large surface area in this region, the baffle located in the middle can maintain structural integrity during the welding of mounting members and the like. Further, the configuration of the noise treatment unit no longer requires perforations to be provided on the baffle itself, because the perforations will affect the structural integrity of the baffle.

[0024] In one embodiment, the noise treatment unit includes a mounting member, and the portion of the mounting member near the intermediate chamber is fixed to the housing of the noise treatment unit. Even when welding is performed on the housing, the baffles disposed nearby will provide an additional area to accommodate higher heat during welding and the like.

[0025] In one embodiment, the noise treatment unit includes a plurality of connectors, which are configured to bypass the immediately adjacent chambers to provide a longer flow path and can also change the flow direction by bypassing the immediately adjacent chambers. The connectors are provided with an optimal length for establishing connections between the chambers without extending the connectors along the entire length of the noise treatment unit.

[0026] In one embodiment, at least two connectors passing through the baffle are disposed at positions offset from the axis of the noise treatment unit for achieving optimal accommodation of components without occupying a large space. For example, in one implementation, three connectors are accommodated on the baffle, and the three connectors are disposed at positions offset from the axis of the noise treatment unit, which is generally located at the center of the noise treatment unit.

[0027] In one embodiment, the noise treatment unit is configured for a compact vehicle having a track width in the range of 1200 - 1400 millimeters.

[0028] In one embodiment, the exhaust system includes an exhaust pipe having an outlet portion. The outlet portion includes an extension that extends at least partially into one of the plurality of first chambers. One or more second chambers include an exhaust pipe for discharging gas to the atmosphere. At least one of the outlet portion and the exhaust pipe is provided with perforations configured to diffuse the exhaust gas during entry into and exit from the noise treatment unit.

[0029] In one embodiment, the intermediate chamber is configured to attenuate high-frequency waves in the exhaust gas that are greater than 4000 Hz and cause discomfort to the human ear. In one implementation, the second chamber having a cumulative volume greater than that of the first chamber is configured to attenuate frequency waves in the range of 1500 Hz to 3000 Hz with at least two-directional changes or flow reversals, which generally produce metallic sounds. Thus, by generating the desired necessary exhaust noise, the exhaust gas discharged from the noise treatment unit will be pleasant for riders and passersby.

[0030] Therefore, the exhaust gas released from the IC engine at high speed and passing through the narrow exhaust pipe is effectively attenuated in noise / sound before being discharged into the atmosphere.

[0031] The exhaust system can be implemented in any two-wheeled vehicle or three-wheeled motor vehicle. However, for purposes of illustration and not limitation, the exhaust system, corresponding other advantages, and features are described by the following examples. The arrow set anywhere in the upper right corner of the figure represents the direction with respect to the motor vehicle. Arrow F represents the forward direction, arrow R represents the rearward direction, arrow UW represents the upward direction, and arrow DW represents the downward direction.

[0032] Figure 1Shows a left side view of an exemplary motor vehicle 100 according to an embodiment of the present invention. The motor vehicle 100 includes a frame assembly 105 which is a structural member of the motor vehicle 100. The frame assembly 105 includes a head tube 111 and a main tube 105 (schematically shown in dashed lines) extending downward and backward from the head tube 111. The motor vehicle includes a front wheel 110, a rear wheel 103, a fuel tank 121, and a seat 106. In one embodiment, the frame assembly 105 includes a main tube 112, a down tube (not shown), and one or more seat rails (not shown) extending backward from the main tube 112. The head tube 111 supports a steering shaft (not shown) and a front suspension 114 (only one is visible), and the front suspension 114 is attached to the steering shaft through a lower bracket (not shown). The front suspension 114 supports the front wheel 110. The upper part of the front wheel 110 is covered by a front fender 115, and the front fender 115 is mounted to the front suspension 114 at the end of the steering shaft. The handlebar assembly 108 is fixed to an upper bracket (not shown) and can rotate in two directions to maneuver the motor vehicle 100. A headlight 109, a face shield (not shown), and an instrument panel (not shown) are provided on the upper part of the head tube 111. The down tube can be located in front of the IC engine 101 and extends obliquely downward from the head tube 111. The main tube 112 is located above the IC engine 101 and extends backward from the head tube 111. The IC engine 101 is mounted in the front through the down tube, and the rear of the IC engine 101 is connected to the main tube 112 at the rear part.

[0033] In one embodiment, the fuel tank 121 is mounted on the horizontal part of the main tube 112. The seat rails are coupled to the main tube 112 and extend backward to support the seat 106. A rear swing arm (not shown) is connected to the frame assembly 105 to swing vertically, and the rear wheel 103 is connected to the rear end of the rear swing arm. Generally, the rear swing arm is supported by a single rear suspension or two suspensions 11 (as shown in this embodiment) provided on either side of the motor vehicle 100. A tail light unit (not shown) is provided at the end of the motor vehicle located behind the seat 106. The rear wheel 103 is substantially arranged below the seat 106 and is rotated by the driving force of the IC engine 101, and the driving force is transmitted from the IC engine 101 through a chain drive mechanism (not shown). In another embodiment, a belt drive mechanism, a continuously variable transmission, or an automatic transmission can be used. Further, an electric motor can be provided to assist the IC engine 101 or drive the motor vehicle 100 independently in combination with the IC engine. The exhaust system 102 is connected to the IC engine 101 for discharging the exhaust gas generated by the combustion of the air-fuel mixture. In one embodiment, at least a part of the exhaust system 102 extends toward one side of the motor vehicle 100 and is provided adjacent to the rear wheel 103 (a part of the exhaust system 102 is arranged adjacent to the rear wheel 103, schematically shown in dashed lines).

[0034] Figure 2Shows a right side view of an IC engine 101 provided with an exhaust system 102 according to an embodiment of the present subject matter. The IC engine 101 includes a cylinder head assembly 210 having a cylinder head 203 and a cylinder head cover 202 mounted on top of the cylinder head 203. In one embodiment, the internal combustion engine 101 is a single-cylinder engine. More particularly, in one embodiment, the internal combustion engine 101 is a four-stroke internal combustion engine 101. In other alternative embodiments, the internal combustion engine 101 may include more than one cylinder head, such as multiple cylinders. In one embodiment, the cylinder head 203 of the present subject matter includes one or more ports (not shown in this figure). For example, an exhaust port (not shown in this figure) of the internal combustion engine 101 can discharge / emmit the exhaust gas generated due to the combustion of the air-fuel mixture, and the air-fuel mixture burns inside the combustion chamber (not shown) of the internal combustion engine 101. The gas discharged from the exhaust port is conveyed through an exhaust pipe 215 of the exhaust system 102 of the internal combustion engine 101. In one embodiment, the exhaust pipe 215 includes an inlet opening 201 which is connected to an exhaust port (not shown in this figure) of the internal combustion engine 101 for enabling the departing exhaust gas to travel smoothly. In one embodiment, the exhaust pipe 215 is connected to the cylinder head 203 through a flange member (not shown).

[0035] In one embodiment, the cylinder head 203 of the internal combustion engine 101 is mounted on top of a cylinder block 204. The cylinder block 204 is supported by a crankcase 20. The cylinder head 203 and the cylinder block 204 define a combustion chamber (not shown) and a piston (not shown), and the piston is slidable inside the combustion chamber, thereby implementing a four-stroke. In one embodiment, the exhaust pipe 215 of the present subject matter includes a first bend 208 adjacent to the inlet opening 201 and a second bend 209 farther from the first bend 208. The distance between the first bend 208 and the second bend 209 depends on one or more parameters, which include the diameter of the (multiple) wheels, the wheelbase, the ground clearance of the second bend from the road / ground surface, etc. In one embodiment, the engine 101 includes at least one spark plug (not shown). In one embodiment, the vehicle 100 is a saddle-type vehicle. In another embodiment, the vehicle 100 is a step-through vehicle. The diameter of the wheels and the layout of the vehicle vary according to the above types and other types of vehicles.

[0036] In one embodiment, an air - fuel supply device 220 is connected to an intake port 206 for regulating the supply of air and fuel. The air - fuel supply device can be a combination of a carburetor, a throttle body, and a fuel injector, an electronic carburetor, etc. In one embodiment, the cylinder head assembly 210 may include more than one exhaust port 205. In one embodiment, the cylinder head assembly 210 of the present subject matter has at least one intake port 206 that allows an air - fuel mixture to enter a combustion chamber (not shown). In one embodiment, the cylinder head assembly 210 includes at least one exhaust port 205 disposed on the other side of the intake port 206. In the said embodiment, the intake port 206 is disposed on the rear - facing side of the cylinder head 203, while the exhaust port 205 is disposed on the front - facing side of the cylinder head 203. In other embodiments, the exhaust port 205 may be disposed on the rear - facing side or the downward - facing side of the cylinder head, and the intake port is disposed substantially opposite to the exhaust port.

[0037] In one embodiment, the exhaust pipe 215 includes at least one catalytic converter unit optimally disposed at a predetermined distance from the exhaust port 205 of the cylinder head 203. In one embodiment, the catalytic converter unit is disposed between a first bend 208 and a second bend 209 of the exhaust pipe 215. In one embodiment, the at least one catalytic converter unit is a pre - catalytic converter or an auxiliary catalytic converter, which is disposed upstream of a main catalytic converter (not shown) in the exhaust system of the present subject matter. In an alternative embodiment, the main catalytic converter (not shown) is disposed within a noise reduction device 225 of the exhaust system 102 of the present subject matter. In one embodiment, the closer the catalytic converter unit is to the exhaust port, the higher the efficiency of the catalytic converter unit.

[0038] In one embodiment, the exhaust pipe 215 includes an outlet portion 211 connected to the noise treatment unit 225. The outlet portion 211 may extend into at least a portion of the noise treatment unit 225. Further, a sealing member 204 is provided to serve as a seal between the outlet portion 211 and the noise treatment unit 225 to eliminate any possibility of exhaust gas leakage into the atmosphere. In one embodiment, the sealing member 204 is provided to annularly cover at least a portion of the noise treatment unit 225 and the outlet portion 211. The sealing member 204 is preferably welded. The noise treatment unit 225 extends substantially in a backward direction from the outlet portion 211. As Figure 1 shown, in one embodiment, the noise treatment unit 225 will be disposed adjacent to at least a portion of the rear wheel 103 and below a rear seat pedal (not shown) of the motor vehicle 100.

[0039] FIG. 3(a) shows a schematic view of a noise processing unit 225 according to an embodiment of the present subject matter. The noise processing unit 225 is part of an exhaust system 102 configured to discharge exhaust gases generated during combustion of an air-fuel mixture and configured to reduce / attenuate the noise generated during exhaust gas discharge before discharging the exhaust gases released from an IC engine into the atmosphere.

[0040] The noise processing unit 225 includes a housing 360 (schematically shown in dashed lines) and a plurality of chambers (expansion chambers) formed by a plurality of baffles disposed within the noise processing unit 225. In the described embodiment, a plurality of first chambers, one or more second chambers, and one or more intermediate chambers are provided. In the described implementation, two first chambers 301, 302 are provided, and an outlet portion 211 of the exhaust pipe 215 is connected such that its downstream extension (365) opens into one of the two first chambers 301, 302. The outlet portion 211 is provided with an extension 365, and the extension 365 can be a solid tube or a perforated tube. Further, an intermediate chamber 311 is provided, and the intermediate chamber 311 is formed adjacent to at least one of the first chambers 301, 302. A second chamber 321 is provided after the plurality of first chambers 301, 302. In one implementation, the second chamber 321 is provided at a downstream portion of the noise processing unit 225. The first chamber 301 is formed by a first baffle 331 (between the first baffle and the upstream housing of the noise processing unit 225), and the intermediate chamber 311 is formed between the first baffle 331 and a second baffle 332. The first chamber 302 provided after the intermediate chamber 311 is formed between the second baffle 332 and a third baffle 333. Hereinafter, the first chamber 301 is referred to as a primary first chamber, and the first chamber 302 is referred to as a secondary first chamber. In the current embodiment, the intermediate chamber 311 is physically disposed between the primary first chamber 301 and the secondary first chamber 302, or generally speaking, the intermediate chamber 311 is selectively disposed between the plurality of first chambers 301, 302. Further, the second chamber 321 is formed between the third baffle 333 and an end baffle 335.

[0041] In one embodiment, the volume of the intermediate chamber 311 (or, in the case of more than one intermediate chamber, the cumulative volume of the intermediate chambers) is substantially less than the cumulative volume of the first chambers 301, 302. The volume of the intermediate chamber 311 is also substantially less than the volume (or cumulative volume) of the second chamber 321. The exhaust gas EG entering the noise treatment unit 225 travels through the first chambers 301, 302, then to the intermediate chamber 311, and then to the second chamber 321. The plurality of chambers 301, 302, 311, 321 are configured to effectively reduce the momentum of the exhaust gas entering the muffler 235. In one embodiment, the intermediate chamber 311 with a smaller volume disposed between the primary first chamber 301 and the secondary first chamber 302 is selectively bypassed as the exhaust gas travels through it, and the exhaust gas enters the intermediate chamber 311 after flowing through all of the first chambers 301, 302. The flow of the exhaust gas in the noise treatment unit 225 will be discussed in the subsequent description. In one embodiment, the first chambers 301, 302 are configured to accommodate an additional catalytic converter unit (not shown). The additional catalytic converter unit can serve as a primary catalytic converter or a secondary catalytic converter unit. Since the first chambers 301, 302 are provided with a larger volume, the noise treatment unit can even accommodate a larger primary converter here.

[0042] FIG. 3(b) shows a schematic cross-sectional view of the noise treatment unit 225 according to an embodiment of the present subject matter. The outlet portion 211 extending into the noise treatment unit 225 is provided with an extension portion 366, and the extension portion 366 is provided with a plurality of perforations configured to diffuse the exhaust gas EG entering the noise treatment unit 225. The diffused exhaust gas expands in the primary first chamber 301, thereby experiencing a reduction in momentum and generating exhaust gas EG1 with reduced energy. For example, in one implementation, the chambers separated by baffles and the baffles are assumed to have infinite impedance. The energy of the exhaust gas is reduced because heat dissipation (by conduction or convection) occurs in the first chamber and the expansion causes a reduction in momentum.

[0043] Further, the first connector 341 connects the primary first chamber 301 and the secondary first chamber 302. The term "connector" may include any device for transferring exhaust gas from one chamber to another. In one embodiment, similar to the described embodiment, the connector is a cylindrical member. The first connector 341 is disposed at a position offset from the axis A-A' of the noise treatment unit 225 and the extension 365 to prevent the exhaust gas EG from directly entering the first connector 341 and to enable entry after expansion. The first connector 341 passes through the intermediate chamber 311, bypassing any exhaust gas flow entering the intermediate chamber 311 from the primary first chamber 301. The first connector 341 passes through the first baffle 331 and the second baffle 332 and is supported by them. After the exhaust gas EG1 reaches the secondary first chamber 302, it undergoes further expansion due to the larger volume of the secondary first chamber 302. In one implementation, the secondary first chamber 302 is provided with a volume larger than that of the primary first chamber 301. The exhaust gas EG1 in the secondary expansion chamber 302 undergoes a further reduction in momentum, especially due to the change in the flow direction, resulting in the exhaust gas EG2 with reduced energy. In the secondary first chamber 302 of the current embodiment, the exhaust gas is guided to flow in a direction opposite to the direction in which it enters the noise treatment unit 225.

[0044] The noise treatment unit 225 is provided with a second connector 342 for connecting the secondary first chamber 302 to the intermediate chamber 311. The second connector 342 and the first connector 341 are disposed at positions offset from the axis A-A' of the noise treatment unit 225 for optimal packaging. The exhaust gas EG2 entering the intermediate chamber 311 has passed through two large expansion chambers, and the intermediate chamber 311 with a smaller volume is configured to attenuate any high-frequency waves of the exhaust gas, resulting in the exhaust gas EG3 with further reduced energy. Subsequently, due to the third connector 343 connecting the intermediate chamber 311 and the second chamber 321, which is physically disposed after the secondary first chamber 302, the exhaust gas EG3 undergoes a change in the flow direction. The third connector 343 is supported by the second baffle 332 and the third baffle 343. The exhaust gas flow entering the second chamber 321 realigns the exhaust gas into the initial flow direction.

[0045] The third connector 343 bypasses the secondary first chamber 302, thereby enabling gas to enter the second chamber 321 to attenuate any remaining higher frequency waves, thereby producing exhaust gas EG4 with further noise attenuation. In one embodiment, the third connector 343, the second connector 342, and the first connector 341 are disposed at positions offset from the axis A-A' of the noise treatment unit 225. This enables the connectors 341, 342, 343 to be effectively or optimally encapsulated on the second baffle 332. The second chamber 321 is provided with a discharge pipe 345 configured to discharge the exhaust gas EG5 from the exhaust system 102 to the atmosphere. In one implementation, the exhaust gas discharge pipe 345 is provided with perforations for the final diffusion of the exhaust gas. Thus, the exhaust gas EG5 leaving the noise treatment unit 225 is attenuated substantially at all frequencies, as Figure 4 shown by curve B. Curve B represents an exemplary graph plotted for noise attenuation across different frequencies according to an embodiment of the present subject matter. It can be seen that curve B does not include any sudden surges or sudden rises and falls and relatively significant attenuation of the noise across different frequencies.

[0046] The noise treatment unit 225 includes an intermediate chamber 311, where the baffles 331, 332 are substantially closer and are disposed at approximately the middle of the noise treatment unit 225, thereby providing the necessary structural rigidity at the middle to support the entire noise treatment unit 225. In one embodiment, the middle is a part of the noise treatment unit 225 that forms 50% of its middle region. In one embodiment, the mounting member 350 is disposed near the intermediate chamber 311. Thus, during welding the mounting member 350 to the housing 360, due to the presence of the baffles 331, 332, the total surface area in this region is larger, thereby reducing the effect of heat on the noise treatment unit 225. Thus, any adverse effect on the material properties of the noise treatment unit is minimal, making the structure rigid. The noise treatment unit can be mounted using a single mounting member 350. However, in another implementation, more than one mounting member can be used if required. As shown in FIG. 3(b), the chambers 301, 302, 311, 321 are disposed adjacent to each other along the axis A-A' of the noise treatment unit 225 without increasing the width of the noise treatment unit 225 (when viewed from the side, the overall cross-sectional area and especially the overall cross-sectional area in the vertical direction do not increase), so as to be mounted on a motor vehicle with a smaller wheelbase, such as a wheelbase in the range of 1200 to 1400 millimeters. Further, the noise treatment unit 225 will not affect the compact layout and the required position of the rear seat pedal, thereby avoiding any layout or design changes.

[0047] FIG. 3(c) depicts another cross-sectional perspective view of the noise processing unit 225 according to an embodiment of the present subject matter. FIG. 3(d) shows an enlarged view of a portion of the noise processing unit 225 according to an embodiment of the present subject matter as shown in FIG. 3(c). The exhaust gas initially flows into the larger first chambers 301, 302, which causes the exhaust gas entering at high speed to expand and initially suppress certain frequency waves. Further, the baffles 331, 332, 333 are configured to provide destructive interference to cancel out the unwanted sound frequencies generated during the combustion process. Further, the first chambers 301, 302, which have an intermediate chamber 311 selectively disposed therebetween, provide a longer travel path for the exhaust gas within the first chambers 301, 302 and pass through the first connector 341 with a longer length, thereby obtaining a longer flow path, so that energy can be absorbed through the dissipation of heat and the attenuation of sound. The noise processing unit 225 with a longer flow path eliminates the unwanted noise / sound. Further, the intermediate chamber 331 selectively physically disposed between the first chambers 301, 302, and the flow that enters the intermediate chamber 311 after passing through all the first chambers 301, 302, can achieve at least two reversals of the flow direction, thereby further slowing down the exhaust gas and enabling a higher transmission loss, resulting in noise reduction. The change in surface area provides resistance to the flow of the exhaust gas, and the exhaust gas reflects a part of its intensity in the form of sound waves in a direction opposite to its travel direction, i.e., sound waves with a relative phase are generated. The reflected sound waves with a relative phase cancel out the initial sound waves of the exhaust gas, thereby reducing the exhaust sound to the desired exhaust sound. In one embodiment, in order to further achieve the diffusion of the exhaust gas, the connectors 341, 342, 343 may be provided with perforations, which in combination with the construction of the muffler achieve effective attenuation of the noise.

[0048] The muffler of the exhaust system with a muffler is designed such that it occupies the minimum space on a motor vehicle, thereby eliminating the need for layout modification. The number of expansion chambers can be increased or decreased as needed. This exhaust system can be used in any type of vehicle including two-wheeled or three-wheeled motor vehicles or even in multi-wheeled vehicles with a compact layout.

[0049] Although certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, variations, and equivalents will now occur to those skilled in the art. Accordingly, it is to be understood that the appended claims are intended to cover all such modifications and variations that fall within the true spirit of the claimed subject matter.

[0050] List of reference signs:

[0051] 100 Vehicle

[0052] 101 IC Engine

[0053] 102 Exhaust system

[0054] 103 Rear wheel

[0055] 105 Frame assembly

[0056] 106 Seat

[0057] 108 Handlebar assembly

[0058] 109 Headlight

[0059] 110 Front wheel

[0060] 111 Head tube

[0061] 112 Main tube

[0062] 114 Front suspension

[0063] 115 Front fender

[0064] 116 Chain drive mechanism

[0065] 11 Rear suspension

[0066] 121 Fuel tank

[0067] 201 Inlet section

[0068] 202 Cylinder head cover

[0069] 203 Cylinder head

[0070] 204 Sealing member

[0071] 205 Exhaust port

[0072] 206 Intake port

[0073] 207 Crankcase

[0074] 208 First bend

[0075] 209 Second bend

[0076] 210 Cylinder head assembly

[0077] 211 Outlet section

[0078] 215 Exhaust pipe

[0079] 220 Air-fuel supply device

[0080] 301 Primary first chamber

[0081] 302 Secondary first chamber

[0082] 311 Intermediate chamber

[0083] 321 Second chamber

[0084] 331 First baffle

[0085] 332 Second baffle

[0086] 333 Third baffle

[0087] 335 End baffle

[0088] 341 First connector

[0089] 342 Second connector

[0090] 343 Third connector

[0091] 345 Discharge pipe

[0092] 350 Mounting member

[0093] 360 Housing

[0094] 365 Extension

[0095] 366 Extension (perforated)

[0096] EG / EG1 / EG2 / EG3 / EG / EG4 / EG5 Exhaust gas

Claims

1. A noise treatment unit (225) for a motor vehicle (100), wherein the noise treatment unit (225) is part of an exhaust system (102) that is functionally connected to an internal combustion engine (101) of the motor vehicle (100), and the noise treatment unit (225) comprises: a plurality of first chambers (301, 302), wherein one of the plurality of first chambers (301, 302) is configured to receive exhaust gas from the internal combustion engine (101); a plurality of second chambers (321), wherein the plurality of second chambers (321) are arranged to be adjacent to the plurality of first chambers (301, 302) at a downstream portion of the noise treatment unit (225); and a plurality of intermediate chambers (311), wherein the plurality of intermediate chambers (311) are arranged between the plurality of first chambers (301, 302), and the noise treatment unit (225) is configured to direct exhaust gas (EG1, EG2) to flow from the plurality of first chambers (301, 302) to the plurality of intermediate chambers (311), wherein the plurality of intermediate chambers (311) are configured to direct exhaust gas (EG3) to flow to the plurality of second chambers (321); the plurality of intermediate chambers (311) are formed by a first baffle (331) and a second baffle (332) arranged in the vicinity of each other; and wherein the plurality of intermediate chambers (311) include a cumulative volume that is smaller than the cumulative volume of the plurality of first chambers (301, 302), and the cumulative volume of the plurality of intermediate chambers (311) is smaller than the cumulative volume of the plurality of second chambers (321).

2. The noise treatment unit (225) for the motor vehicle (100) according to claim 1, wherein the plurality of intermediate chambers (311) are configured to change the flow direction of the exhaust gas (EG2) in two or more directions.

3. The noise treatment unit (225) for the motor vehicle (100) according to claim 1, wherein the plurality of first chambers (301, 302), the plurality of intermediate chambers (311), and the plurality of second chambers (321) are adjacently arranged along an axis (A - A') of the noise treatment unit (225), and the axis (A - A') passes through a central portion of the noise treatment unit (225) in a front - to - rear direction with respect to the motor vehicle (100).

4. The noise treatment unit (225) for the motor vehicle (100) according to claim 1, wherein the plurality of intermediate chambers (311) are arranged at a middle portion of the noise treatment unit (225).

5. The noise treatment unit (225) for the motor vehicle (100) according to claim 1, wherein the noise treatment unit (225) includes a mounting member (350), and the mounting member (350) is fixed to a housing (360) of the noise treatment unit (225) at a portion near the intermediate chamber (311).

6. The noise treatment unit (225) for the motor vehicle (100) as claimed in claim 1, wherein the plurality of first chambers (301, 302) includes a primary first chamber (301) and a secondary first chamber (302), and wherein the primary first chamber (301) and the secondary first chamber (302) are connected by a first connector (341) bypassing the intermediate chamber (311).

7. The noise treatment unit (225) for the motor vehicle (100) as claimed in claim 6, wherein the noise treatment unit (225) includes a second connector (342) and a third connector (343), the second connector (342) being configured to connect the secondary first chamber (302) to the plurality of intermediate chambers (311), the third connector (343) connecting the plurality of intermediate chambers (311) to one of the plurality of second chambers (321), the third connector (343) passing through a third baffle (333) forming one of the plurality of second chambers (321).

8. The noise treatment unit (225) for the motor vehicle (100) as claimed in claim 6, wherein the noise treatment unit (225) includes at least two of the first connector (341), the second connector (342) and the third connector (343) disposed at positions offset from the axis (A - A’) of the noise treatment unit (225).

9. The noise treatment unit (225) for the motor vehicle (100) as claimed in claim 1, the motor vehicle (100) including a track width ranging from 1200 millimeters to 1400 millimeters.

10. The noise treatment unit (225) for the motor vehicle (100) as claimed in claim 1, the exhaust system (102) including an exhaust pipe (215) having an outlet portion (211), the outlet portion (211) including an extension (366) extending into one of the plurality of first chambers (301, 302), and the plurality of second chambers (321) including a discharge pipe (345), and wherein at least one of the outlet portion (211) and the discharge pipe (345) is provided with perforations.

11. A method for treating exhaust gas (EG) by a noise treatment unit (225), the method comprising the steps of: passing exhaust gas (EG, EG1, EG2) through the plurality of first chambers (301, 302) of the noise treatment unit (225); passing exhaust gas (EG3) through the plurality of intermediate chambers (311), the plurality of intermediate chambers (311) being disposed between the plurality of first chambers (301, 302); and guiding exhaust gas (EG4) through the plurality of second chambers (321), the plurality of second chambers (321) being arranged adjacent to the plurality of first chambers (301, 302) at a downstream portion of the noise treatment unit (225); the plurality of intermediate chambers (311) being formed by a first baffle (331) and a second baffle (332) disposed in proximity to each other; and Wherein the plurality of intermediate chambers (311) include a cumulative volume that is less than the cumulative volume of the plurality of first chambers (301, 302), and the cumulative volume of the plurality of intermediate chambers (311) is less than the cumulative volume of the plurality of second chambers (321).

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